Potential conditions, in the English speaking world also known under the name “future less vivid” (for a critique of that particular term, see here), are conditional sentences that talk about supposed events, and what the consequences of such events would be, e.g.
Hic ego si finem faciam dicendi, satis fidei et diligentiae meae [⋯] fecisse videar.
Besides the present subjunctive, the perfect subjunctive is also possible. Allen & Greenough claim:
If the conditional act is regarded as completed before that of the apodosis begins, the perfect subjunctive [is substituted in the protasis] for the present subjunctive.
⋯ and offer this example:
Sī ā corōnā relictus sim, nōn queam dīcere. (Brut. 192)
If I should be deserted by the circle of listeners, I should not be able to speak.
However, the German grammars I have all claim there is no difference in meaning between present and perfect subjunctive, and offer examples with the perfect subjunctive in the apodosis as well. See this grammar for Gymnasium students, for example, which offers:
Si magister sero veniat/venerit, discipuli gaudeant/gavisi sint.
So my question is:
- Is there a difference in meaning, or in nuance, in conditional sentences between perfect and present subjunctive?
- Is the perfect subjunctive regularly used in the apodosis?